This invention relates to a high-efficiency electric cooker intended more particularly for restaurants or canteens.
At the present time there is no device on the market capable of guaranteeing satisfactory and fast cooking of sized and deep-frozen meats of the kind daily distributed in large quantities to large-area users or high-output restaurants on the lines of the American fast food restaurants.
The object of the invention is to fill this gap by providing a device capable of rapid and efficient cooking both of hamburgers and other foods such as grills, eggs, sausages, bread, etc., while complying with the rules of elementary hygiene.
Another object of the invention is to provide a device of the above type which is extremely simple to use and with no risks to the professional or the user, and of minimum cost in respect of manufacture, servicing and maintenance.
The device comprises conventionally a conductive surface resting on a mounting and co-operating with heating means and with electronically controlled temperature control means.
The device is characterised in that the heating means comprise heating resistances detachably locked between the conductive surface and a retaining surface of similar shape and dimensions situated beneath the conductive surface, and are connected by supply leads to standard commercial electrical components wired to plug-in bases and disposed in a control drawer filled on the mounting of the device, closed by a cowl at the rear and provided, at the front, with a control panel enabling the supply to the heating resistances to be controlled.
According to the invention, the term "surface" should be considered in a very wide sense and although the device is more generally in the form of a flat grill-type cooking surface it may in some cases comprise a hollow device intended to receive frying oil.
The main feature of the device according to the invention is linked to the presence of the control drawer, which contains only standard components which can therefore be very easily replaced in the event of breakdown. Also, in the event of major electrical problems on the equipment the drawer can be instantaneously replaced by an identical pre-connected drawer without any interruption to operation, something which could be very disadvantageous particularly in a restaurant.
All the operations on the electrical components in the drawer are generally carried out from the rear of the device (by opening the cowl). To facilitate access to these different components it is advantageous to incline them slightly upwards from the rear part.
According to the invention, the control drawer will usually be made from a sheet metal, more particularly a 15/10 solid stainless steel sheet for the facing elements (rear cowl and control panel) and perforated for the base so as to provide good ventilation of the interior.
According to another feature of the invention, the temperature control means comprise at least one probe disposed in a bore provided for this purpose in the conductive surface and cooperating with standard commercial electronic controllers disposed in the control drawer
As a result, the control drawer contains all the "drive" for the device. To guarantee user safety, and particularly the safety of the maintenance personnel, according to another feature of the invention, it comprises a safety switch mounted in the control drawer and breaking the power supply to all the electrical components and electronic components in the event of the drawer being opened.
To improve the efficiency of the device according to the invention, there must be optimum utilization of the energy transmitted to the conductive surface by the heating resistances and the heat losses must be minimized as far as possible.
To meet the first of these requirements, the conductive surface is preferably formed by a chromium plated metal horizontal hot plate polished to give it a mirror finish.
For example, it is possible to use a polished steel plate 18 mm thick which has had a 60 micron pure chromium surface treatment and then been repolished to bring it to 50 microns. The result of this treatment is to give the plate an irradiating effect and hence improve its performance.
On the same lines, to obtain satisfactory results, the performance of the hot plate should be identical at every point on its surface. To this end, the fact that the maximum heat dissipation occurs at the edges of the plate must be taken into account by providing more powerful resistances in the lateral part of the plate than in its central part.
By way of example, it has been possible to obtain satisfactory results by providing the plate with 1800 watt lateral resistances and 1500 watt central resistances.
In order to identify and eliminate any risk of confusion of these resistances, particularly in the event of replacement, they are advantageously connected to the control drawer by supply leads of different colours (e.g. red for 1800 watts and 1500 watts).
To reduce the heat losses and obtain perfect heat exchange between the hot plate and the heating resistances, the latter must be locked adequately against the hot plate.
To this end, and according to another feature of the invention, the retaining surface comprises a metal retaining plate, more particularly of steel, of the the same dimensions as the hot plate to which it is pivotally connected by means of at least one and preferably two hinges having hinge pins, at its front part and having, at the rear, at least one and preferably two fixing lugs formed with bores co-operating with similar fixing lugs provided at the rear of the hot plate to receive bolts for fixing the two plates and locking the heating resistances between them.
This feature gives adequate clamping of the two plates and hence good locking of the heating resistances while allowing easy access to the latter, particularly in the event of a breakdown, for replacement purposes, simply by means of the bolts.
According to another feature of the invention, which provides maximum locking or clamping of the resistances at the front between the two plates, the axis of the hinge pins connecting the plates is adjustably inclined to the plane of the plates.
For this adjustment the hinge pins used will often have an eccentric axis and be provided with a diameter adjustment bush.
To improve the efficiency of the device, the energy dissipation via the bottom part of the retaining plate must also be minimized, for which purposes and according to another feature of in invention, the retaining plate is connected by its bottom part to a casing, more particularly a metal casing, containing a thermal insulator, more particularly compressed rock wool.
According to another feature of the invention, the cowl closing the rear part of the control drawer is formed with perforations co-operating with deflectors to allow ventilation of the electrical components and electronic component.
According to another feature of the invention, the top of the mounting has a base to receive the hot plate, said base being hollowed out at the centre and having two longitudinal side slots for the discharge of cooking fat or oil and each communicating with a sealed slide open at the top of the device to receive a fat and oil recovery drawer.
The hot plate is fixed to the base more particularly by welding during manufacture. The assembly formed by the base and the sealed slides preferably forms an integral assembly made from sheet metal, in which the side slots are formed by pressing. These elements will preferably have a rounded shape to facilitate cleaning. For the same purpose, the handles of the fat and oil recovery drawers are preferably made in an integral form with the drawers to give a clean and smooth elevation.
For functional use of the device it is also advantageous to provide the front of the hot plate with a bar, more particularly of tubular stainless steel, to allow th fitting of detachable plates.
Also, the obtain maximum satisfaction, the device should be provided with safety means for monitoring proper operation of each of the heating resistances. Such means may advantageously be indicator lights disposed on the control panel and lighting up automatically for a predetermined time when the device is switched on. Of course, the number of indicator lights provided must be identical to the number of heating resistances.